The objective of this study is to identify the behavioral development of preterm and term infants over the first 18 months of life. The predictive validity of the Brazelton Neonatal Behavioral Assessment will be determined, and the effectiveness of this assessment will be compared to neurologically weighted assessment procedures. Thirty full-term and thirty preterm infants will be used as subjects. All infants will be assessed with Parmelee's set of obstetric, pediatric scales, and his neurological examination during the neonatal period and repeatedly over the next 18 months post term conceptual age. The Brazelton Scale will be administered repeatedly during the neonatal period. Behavioral assessments of cognitive, emotional, and social development, including videotaped face-to-face infant-mother interaction, Uzgiris-Hunt and Bayley Scales, free-field play, and home observations, will be made repeatedly over the first 18 months post term conceptual age. A priori predictions to individual functioning will be made from the newborn period to 3 and 5 months and cumulatively from the first 5 months to 9 and to 18 months. Data analysis of assessed outcome in relationship to the neonatal data and the relationship among the other ages of assessment will provide an evaluation of the predictive power of the assessment strategies for the pattern of an individual infant's development.